This invention relates to a rock breaking cartridge of the type which makes use of a propellant or an energetic composition to generate high pressure gasses which are used for the breaking of rock.
The energetic composition, through its chemical composition and physical characteristics, upon initiation, deflagrates (burns fast) instead of detonating, and it is necessary to confine a resulting pressure wave to allow for pressure build-up in order to break rock.
If an energetic composition is securely confined inside a cartridge housing, then a high pressure build-up occurs inside the housing and ruptures the housing. If this process takes place because of an accidental initiation of the composition then, depending on the circumstances, injury to personnel or damage to equipment can result. Another factor is that strict rules apply to the storage and transport of this type of cartridge.
At least for the aforegoing reasons it is desirable for a rock breaking cartridge to be capable of generating maximum pressure build-up only if the cartridge is in an operative environment. The safety of the cartridge is thereby inherently increased and transport and storage problems are significantly alleviated.
U.S. Pat. No. 3,765,331 describes a water-armed fuse in which a piston directly acts on a water-filled volume to initiate a primer. The pressure exerted on the primer is directly dependent on the area of the piston, a feature which is not always desirable.
The invention aims to provide a rock breaking cartridge which addresses the aforementioned requirements.